1. Field of the Invention
The present invention relates to a hand operated backpack sprayer pump and wand sprayer assembly. Fluid is contained in a tank which is forced into a pressurized vessel, the fluid contained in said vessel is thereby sustained at high pressure which may be released through a sprayer wand having a spring loaded release valve.
2. Discussion of the prior Art
Many patents have been issued covering manually operated backpack sprayers which have a reservoir tank and pressure vessel located therein. U.S. Pat. No. 5,335,853 teaches a compact and long lasting sprayer pump and agitator combination wherein a pump assembly having a dual acting piston reciprocates within a pump cup housing thereby performing the actions of injecting fluids into a pressure vessel as well as forcing fluid through another conduit to agitate the fluid contained in the tank reservoir. U.S. Pat. No. 4,798,333 teaches a portable sprayer having improved combination of a piston and diaphragm pump wherein the piston forces fluid through a cylinder housing into the pressure vessel in combination with a diaphragm assembly which draws fluid in from the tank and injects it back into the tank at high velocity utilizing the same reciprocating action of the piston. U.S. Pat. No. 4,768,714 teaches a portable sprayer with leak control and agitator and similarly has a single action piston which forces fluid into a pressure vessel by additionally having a diaphragm to inject fluid into the tank at high velocity to agitate said fluid. U.S. Pat. No. 4,702,419 teaches a diaphragm pump wherein fluid is forced into the pressure vessel utilizing only the action of a diaphragm securely held at the bottom of a pump cup. The pump assemblies of the prior art generally utilize diaphragms made of a flexible and resilient material which provides an adequate seal between the piston and the lower pump assembly. However, the diaphragms, after continued use, develop cracks, leaks and various other points which are suspectable to fluid leakage. Additionally, most pump assemblies taught in the prior art utilize steel or other metals which add to the weight of the pump assembly, an undesirable characteristic as the entire sprayer is to be carried on the back of an individual. Pump assemblies of the prior art which do not utilize a diaphragm have typically also posed an additional problem of leakage along the cylinder rod after extended use and do not provide an adequate means of preventing said leakage. In addition, pressure in the pressure vessel may be increased by each action of the manually operated lever until such time as the pressure seals within the pressure vessel give way or until a pressure release valve is activated. However, there is no means to adjust the maximum pressure which is contained within the pressure vessel thereby controlling the internal pressure of the pressure vessel as well as the spray pressure and velocity of fluid ejected from the sprayer wand.